Acid rain is caused by the pollution of environment by
Answer & explanation
Answer: (d) nitrous oxide and sulphur dioxide
Acid rain forms when sulphur dioxide and oxides of nitrogen are released into the air. These gases react with water and oxygen to form sulphuric and nitric acids, which fall as acidic rain. Option (d) is the only one that pairs sulphur dioxide with an oxide of nitrogen.
- ✗ (a) Carbon dioxide is a greenhouse gas. It makes even clean rain only slightly acidic (carbonic acid), not acid rain. Nitrogen gas (N2) is largely inert and does not cause acid rain.
- ✗ (b) Carbon monoxide is a toxic gas from incomplete combustion. Neither it nor carbon dioxide produces the strong acids behind acid rain.
- ✗ (c) Ozone near the ground is a pollutant and a component of smog, and carbon dioxide is a greenhouse gas. Neither is a major acid-rain precursor.
- ✓ (d) Sulphur dioxide and oxides of nitrogen are the pollutants that cause acid rain. They form sulphuric and nitric acids in the atmosphere. This is the only option naming sulphur dioxide together with an oxide of nitrogen.
Remember · Acid rain = SO2 + NOx (mainly from burning fossil fuels) forming sulphuric and nitric acids. Rain with pH below 5.6 is called acid rain.
📘 Read it in NCERT: Class 11 Political Theory, Ch 3 (practise this chapter) · Class 10 Science, Ch 2 (practise this chapter)
Sources
- NCERT Class 11 · Political Theory, Chapter 3 “They also account for three-quarters of emissions of sulphur and nitrogen oxide that cause acid rain.”
- NCERT Class 10 · Science, Chapter 2 “When pH of rain water is less than 5.6, it is called acid rain.”
- US EPA – What is Acid Rain? ↗ “Acid rain results when sulfur dioxide (SO 2 ) and nitrogen oxides (NO X ) are emitted into the atmosphere and transported by wind and air currents.”
Question: UPSC Civil Services (Preliminary) 2013, General Studies Paper I. Explanation: Minimalist IAS, checked 25 Oct 2026 (how we verify). ·
